The present invention relates to a liquid-sealed mount.
In a working vehicle such as a hydraulic shovel, a cab is mounted on a vehicle body frame via a liquid-sealed mount to reduce transmissibility of vibrations and impacts, which occur during a working operation and traveling, to a cab.
FIG. 10 is a sectional view showing a first example of a conventional liquid-sealed mount. A damping member 34 attached at a lower end of a stud 33 is housed inside a cylindrical case 31 having a bottom face. The dumping member 34 is formed into a disc-shape having a little smaller diameter than an inner diameter of the case 31 to form a ring-shaped clearance between an outer circumferential portion thereof and the case 31. The stud 33 is attached at a position of an axis of a cylindrical elastic body 36 inserted in the case 31, and is held by the case 31 via the cylindrical elastic body 36. A recessed portion 36a is formed on an undersurface of the elastic body 36. A viscous liquid L is sealed up to a midpoint of the recessed portion 36a inside the case 31 sealed by the elastic body 36, and an air chamber sealed by the viscous liquid L is formed in an upper part in the recessed portion 36a. 
The case 31 and the stud 33 are mounted to either the cab or the vehicle body frame, respectively. Vibrations and impacts occurring to the vehicle relatively move the case 31 and the stud 33, and the damping member 34 agitates the viscous liquid L. A damping force occurring at this time causes a buffering action to work, which reduces the vibrations and impacts transmitted to the cab.
FIG. 11 shows a second example of the conventional liquid-sealed mount, which is a sectional view showing a liquid-sealed mount disclosed in Japanese Patent Laid-open No. 7-127683 that can prevent breakage of an elastic body even when a large load acts thereon to cause a large displacement.
A damping member 44 attached to a lower end of a stud 43 is housed inside a cylindrical case 41 having a bottom face. The damping member 44, which has an orifice hole 44a vertically penetrating it, forms a disc-shape having a little smaller diameter than an inner diameter of the case 41, and a ring-shaped clearance is formed between an outer circumferential portion thereof and the case 41. A coil spring 48 is provided between the case 41 and the damping member 44, and upper and lower ends thereof are connected to the bottom face of the case 41 and the damping member 44, respectively. A sleeve 47 is attached to an inner circumference of a cylindrical elastic body 46 attached in an upper part of the case 41, and the stud 43 is hermetically in contact with an inner circumference of the sleeve 47 and is held to be vertically slidable. A bellows 49 is integrally formed at a lower end of the elastic body 46, and a lower end portion of the bellows 49 is hermetically attached to an attached portion of the damping member 44 and the stud 43. The viscous liquid L is scaled inside the case 41 sealed by the elastic body 46, the bellows 49 and the damping member 44.
Even if a large load acts on the stud 43, it is supported by the spring 48 and the load does not act on the elastic body 46, and therefore breakage of the elastic body 46 can be prevented. Cushioning, in a vertical direction is performed by the dumping member 44 and the spring 48, and cushioning in a lateral direction is performed by the elastic body 46. Both of the cushioning actions reduce the vibrations and impacts transmitted to the cab.
However, the above-described conventional liquid-sealed mount has the following disadvantages.
The damping force is caused by pressure loss of the viscous liquid L which is throttled in the clearance from the cases 31 and 41 due to a pressure difference between upper sides and lower sides to the damping members 34 and 44 to flow. Consequently, in the direction in which the studs 33 and 43 descend, the lower sides of the damping members 34 and 44 are at high pressure and the pressure difference from the upper side becomes large, thus making it possible to obtain a large damping force. However, in the direction in which the studs 33 and 43 ascend, the air inside the recessed portion 36a is compressed in the first example of the prior art, and the air inside the bellows 49 is compressed to contract the bellows 49 in the second example of the prior art. Therefore, the upper sides of the damping members 34 and 44 are never at sufficient high pressure. Consequently, the pressure differences between the upper sides and the lower sides of the damping members 34 and 44 cannot be sufficiently large, and the damping force is reduced.
Further, when a large load in a rising direction is exerted on the studs 33 and 43, the pressure in the upper sides of the damping members 34 and 44 do not become sufficiently high, and the pressure differences corresponding to the load occur between both sides of the damping members 34 and 44. As a result, the pressure in the lower sides of the damping members 34 and 44 is reduced to cause cavitation, and the flow of the viscous liquid L flowing through the aforementioned clearance is extremely reduced, thus reducing the damping force to a large extent.
To eliminate the above-described disadvantage, the present invention has its object to provide a liquid-sealed mount, which is capable of obtaining excellent damping performance.
In order to attain the above-described object, the liquid-scaled mount according to the present invention has a constitution including
an elastic body,
a stud penetrating through the elastic body;
a case, which is in a cylindrical shape with one end side being opened and with a bottom face on the other end side, houses a viscous liquid in an inside thereof, and which the viscous liquid is sealed in by fitting the elastic body and the stud into the opening at the one end side, and
a damping member attached to the stud in a state in which the damping member submerges in the viscous liquid,
wherein a wall surface of a portion, which submerges in the viscous liquid, of the case is formed so that an inner diameter gradually decreases toward a lower position and an angle of inclination is different in an upper part from a lower part, and an outer circumferential side surface of the damping member opposes the inclined surface of the case.
According to the above constitution, the clearance between the case and the outer circumferential side surface of the damping member is gradually narrowed following the descent of the stud (namely, the descent of the damping member), and therefore the damping force caused by pressure loss of the viscous liquid passing through this clearance can be smoothly made larger, and a large damping force can be obtained according to the vibration width, namely, when the width of vibration is large. Further, the angle of inclination of the inclined surface of the case is formed in a plurality of stages, whereby the damping force can be changed in the multiple stages, and therefore the impact that occurs at the time of abutment against the stopper can be cushioned by setting the damping force to be large before the stud or the like abuts against the stopper. The damping force can be set optionally by optionally setting a plurality of angles of inclination of the case.
Further, in the liquid sealed mount, the constitution in which an outer diameter of the damping member is larger in a lower part than in an upper part may be suitable. According to the above constitution, for the vibration in the lateral direction, which oscillates the upper end portion of the stud, the resultant force of the reaction force, which controls and diminishes the vibration, acts on the lower part of the damping member, and thus a profound vibration controlling effect can be obtained.